[BUGFIX] Fix unit tests for TaskExecutor

Resolves: #60296
Releases: 6.1
Change-Id: Ic4b237a3589a82ef9f870221ef930e0a182e1c85
Reviewed-on: http://review.typo3.org/33496
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>